Among many resin compounds are epoxy resin compounds consisting of epoxy resin, hardener, inorganic filler, and other additives. They find general use its molding materials on account of good electrical and mechanical characteristics.
Resin compounds such as phenolic, silicone and epoxy resin compounds are commonly used for sealing semiconductor devices, because they offer higher productivity and lower production cost than any other sealing materials. Of these resin compounds, epoxy-based ones are predominant because of their low price, good productivity, and balanced properties. Resin sealing by the conventional technology, however, involves many practical problems as the result of the recent semiconductor technology tending toward larger and thinner packages provided with more pins than before. A typical example of such problems is associated with molding. That is, the sealing of large packages with a conventional resin compound causes a short shot to occur (at the time of transfer molding) which leads to such defects as pinholes. Similarly, the sealing of multiple-pin packages suffers resin peeling due to incomplete adhesion. Moreover, thinner packages present difficulties in sealing with conventional resin compounds because they offer only a limited allowance for the dislocation of the chip and its wires that occurs at the time of sealing.
In order to address these problems, there have been proposed several methods for improving the flowability of the resin compounds. One way to achieve this object is by the lowering of viscosity through reduction of inorganic filler, change of gel time, and modification of the resin itself. It turned out, however, that these measures do not meet all the requirements for the strength and glass transition point of resins, the reliability of semiconductor devices at high temperature and humidity, the resistance of package to cracking due to soldering heat, and the molding cycle governing productivity. Any attempt to improve flowability often ends up with the clogging of vent holes by the resin compound which has entered the mold after repeated transfer molding.
An attempt has been made to improve the flowability of resin compounds at the time of molding by specifying the particle shape of inorganic filler. It is successful in achieving its original object but is not successful in improving reliability at high humidity and resistance to soldering heat and also improving moldability, thereby eliminating resin peeling.
There is disclosed in European Patent Laid-open No. 0,450,944 an epoxy resin compound composed of a biphenyl-skeleton epoxy resin, a hardener, and silica with a specific particle size. This epoxy resin compound is claimed to have improved resistance to soldering heat. Nevertheless, it does not completely solve the above-mentioned problems.
With the technical background mentioned above, the present invention was completed to achieve the following objects.
(1) To provide a semiconductor device comprising a semiconductor element sealed with a new epoxy resin compound which has a low melt viscosity, causes no vent hole clogging after repeated molding operation, and yields molded products free of resin peeling, pinholes, and stage shift. PA1 (2) To provide a semiconductor device comprising a semiconductor element sealed with a new epoxy resin compound which, when used as a sealing material, yields semiconductor devices having improved reliability at high temperature and humidity and good resistance to soldering heat.